1. Field of the Invention
The present invention relates to an electronic timepiece having a calendar device which uses a rotating date indication panel or a date dial.
2. Description of the Related Art
In common calendar systems for a conventional wrist watch with a calendar, a date dial is driven by a date dial driving wheel which makes one complete rotation every twenty-four hours, and which constitutes a known date drive gear train interlocked with a time indication gear train. Therefore, changing date indication may require about two hours of advancement time.
It has also conventionally been proposed that an analog indication watch employs a Geneva mechanism for advancement and stabilization of a date dial. In one technique proposed, for example, in Japanese Patent Publication No. Hei 6-27880, a Geneva wheel is provided, which is continuously driven by a continuously driven hand gear train, so as to intermittently rotate a date dial driving wheel for advancing a date dial.
According to this proposal, however, the Geneva wheel, the rotation of which is based on the rotation velocity of the hand gear train, rotates only at a slow speed. Therefore, as much as ten to twenty minutes are required to fully advance the date dial. As a result, rotation restraint applied to the date dial driving wheel by the flange of the Geneva wheel may fail, causing improper movement of the date dial when external shock is applied to the timepiece during such a large amount of time for advancement, during which the date dial driving wheel is driven by the feed tooth of the Geneva wheel.
Meanwhile, positioning for conventional rotation restraint imposed on the date dial has been achieved using a bounding restraint lever. The date dial is pressed with a larger force as it is driven for date change until the force peaks when a tooth of the gear of the date dial passes over the apex of a convex of the bounding restraint lever.
In a method for driving a date dial by using a date dial driving wheel, which is rotated by a date drive gear train, date change can be successfully achieved irrespective of variation of the pressing force onto the date dial by the bounding restraint lever because the rotation torque of the date dial driving wheel is sufficiently large.
In either case, however, too much time is required to change dates and the period of no-date indication between adjacent date indications, during which the present date indication cannot be easily read, remains too long.
In order to solve the above problems, various proposals have been made to reduce a date dial advancement time to facilitate date indication reading. One proposal is such that a date advancement nail, which constitutes a date dial driving wheel making one complete rotation for twenty-four hours, is instantly activated so that the date dial is advanced instantly. Such a date dial driving wheel, however, has problems including complicated structure, increased cost, and thick movements resulting from a required large cross sectional arrangement size for a date dial driving wheel, a date dial, and associated members.
Another proposal is such that, in a conventional calendar mechanism having a date dial driving wheel, which makes one complete rotation for twenty-hour hours, an indication wheel (a date dial) is driven using a date advancement transducer (a date step motor) dedicated to drive the date dial (an indication wheel), an electronic circuit for drive-controlling the date step motor, a gear train, and a drive wheel.
Specifically, in a preferred embodiment disclosed in Japanese Utility Laid-open No. Hei 4-124494, a step motor is driven in response to a drive pulse from an electronic circuit to transmit rotation via a gear train to a drive wheel to drive an indication wheel. Also, under control by the electronic circuit, a pulse in an opposite direction from that of the drive pulse is output when completing the drive so that right and left backlash of the drive and indication wheels is equalized. With this arrangement, date dial advancement time is reduced and the date indication can be read more easily.
However, a calendar mechanism in which respective members of a date step motor, in particular, a series of components from a rotor to a date dial, constitute a slowdown gear train, has the following problems.
That is, since the date dial is kept positioned utilizing magnetic retention of a rotor which constitutes a date step motor, the date dial may be displaced from its stationary stabilized position when it receives external disturbance (including shock due to a swinging arm) and thereby generates inertial force resulting in rotating the rotor via the interlocked slowdown gear train.
Also, date indication may move off a date window (not shown) formed on a dial plate when the date dial is caused to rotate due to applied external disturbance by an amount equivalent to the sum of meshing backlash caused in the respective members of the slowdown gear train, i.e., those from the date dial to the rotor.
The present invention has been conceived to overcome the above problems and aims to provide an electronic timepiece having a calendar advancement device capable of correcting a date dial in a short time, and resistant to external shock.
In order to achieve the above objects, according to one aspect of the present invention, there is provided an electronic timepiece having a date dial as a rotating indication panel for dates on a calendar, comprising: a calendar advancement device, including a 24-hour switch for generating a date dial drive signal for every twenty-four hours; a date dial advancement transducer activated by a control circuit having received the date dial drive signal; and a date advancement mechanism having a date dial stabilizing Geneva wheel, and a date dial driving wheel for engagement with a flange of the Geneva wheel and a date wheel gear of the date dial, and being activated with force from the date dial advancement transducer.
With the above arrangement, the Geneva wheel is rotated quickly by the date dial advancement transducer to update dates so that a date change time and chance for erroneous operation of the date dial due to external shock can be reduced.
Also, the above electronic time piece may further comprise a detection mechanism for detecting start to advance the date dial; a counter circuit for counting for a predetermined amount of time in response to a signal from the detection mechanism; and a control circuit for suspending the date dial advancement transducer based on an output from the counter circuit to thereby suspend rotation of the date dial stabilizing Geneva wheel.
With the above arrangement, a constant stop position for the Geneva wheel can be achieved using the counter circuit. This can ensure stabilization of the date dial.
Further, in the above electronic timepiece, a feed tooth of the date dial stabilizing Geneva wheel may be located in a region opposite from the date dial driving wheel when the date dial is in a stabilized state.
With the above arrangement, the date dial can be further stabilized, and movement of the date dial in forward or backward direction can be handled in a similar manner.
Still further, the above electronic timepiece may further comprise a control circuit for fast-forward-rotating the date dial advancement transducer during a period from activation of the date dial advancement transducer to at least abutment of a feed tooth of the date dial stabilizing Geneva wheel on teeth of the date dial driving wheel.
With the above arrangement, time without load can be reduced so that a date change time can be further reduced. Also, movement of the date dial can be easily assured when the transducer is not rotated quickly.
Still further, the above electronic timepiece may further comprise a control circuit for fast-forward-rotating the date dial advancement transducer for correction of the calendar during a period from activation to stoppage of the date dial advancement transducer.
With the above arrangement, correction can be more quickly achieved.
Still further, it is possible to configure the above electronic timepiece so that abutment of the feed tooth of the date dial stabilizing Geneva wheel on the teeth of the date dial driving wheel is judged from a number counted by the counter circuit.
With the above arrangement, the need for any special abutment detection mechanism other than a counter circuit can be eliminated.
Still further, in the above electronic timepiece, abutment of the feed tooth of the date dial stabilizing Geneva wheel on the teeth of the date dial driving wheel may be detected from a signal from a detection mechanism for detecting start to advance the date dial.
With the above arrangement, operation can be carried out at reliable timing.
Still further, in the above electronic timepiece, the detection mechanism for detecting start to advance the date dial may have a pattern provided on the date dial and a photo sensor for detecting the pattern.
With the above arrangement, there is provided a prompt and sensitive detection mechanism.
Still further, in the above electronic timepiece, the detection mechanism for detecting start to advance the date dial may have a load detection circuit for detecting load on a drive circuit for the date dial advancement transducer.
With the above, a simpler structure can be achieved.
It is also possible to configure the above electronic timepiece such that the feed tooth of the date dial stabilizing Geneva wheel is held in a position, when the date dial is in a stabilized state, which is determined according to a ratio between forward and backward rotation speeds of the date dial advancement transducer so that the correcting of the date dial starts after a substantially same amount of time through either forward or backward rotation.
With the above arrangement, movement of the date dial can be corrected in the same time period through forward or backward rotation.
According to another aspect of the present invention, there is provided an electronic timepiece having a date dial as a rotating indication panel for dates on a calendar, comprising: a control device for dates on a calendar, including a date advancement transducer for driving a date dial; a slow-down gear train for transmitting rotation force of the date advancement transducer to the date dial; a date dial intermittent rotation drive device constituting a part of the slow-down gear train, for intermittently driving the date dial; and a bounding restraint lever for restraining rotation of the date dial in a non-driven state, and releasing rotation restraint on the date dial in a driven state.
With the above arrangement, date dial correction can be achieved in a short time, and the timepiece is more resistant to shock.
Also, in the above electronic timepiece, the bounding restraint lever may be engaged with teeth of the date dial in a non-driven state for rotation restraint, and departs from the teeth of the date dial in a driven state for releasing load due to pressing force applied to the date dial.
With the above arrangement, the timepiece is highly resistant to shock.
Further, the above electronic timepiece may be configured such that the date dial intermittent rotation device includes a date dial driving wheel arranged for engagement with the date dial all the time, a date intermediate wheel having feed teeth for intermittent engagement with the date dial driving wheel, and an eccentric cum for engagement with and rotating the bounding restraint lever, the date intermediate wheel and the eccentric cum having a common rotation center.
With the above arrangement, the bounding restraint lever can be reliably rotated.
Still further, in the above electronic timepiece, a bearing is provide between the eccentric cum and the feed teeth, for receiving an axis of the date intermediate wheel, and, the bounding restraint lever, the eccentric cum, the teeth of the date dial for engagement with the date dial driving wheel are provided on a same plane surface.
With the above, reduction of a correction time for the date dial, and a thin shock-resistive mechanism can be achieved.
According to the above described aspect of the present invention, the date dial is held still a under consistent stabilized condition when it is in a non-driven state (a normal operation) because the date bounding controlling part constrains rotation of the date dial. On the other hand, when the date dial is in a driven state (date change) only a small rotation load torque due to the date dial is applied to the step motor because the date dial is rotated after rotation restraint applied by the date bounding restraint part to the date dial is lifted. In this way, an electronic timepiece with a calendar in stabilized operation condition is provided.